Select a photo, go into the crop tool. The indicated aspect ratio is 3x2 or 2x3, and the photo renders properly in the tool. Exit crop without making changes, and it will appear that the photo now renders properly. However, if you select a different photo, then select the "fixed" one again, it is back to rendering in 4:3.

Now go into the crop tool, select aspect ratio, and select Original. Select the check mark to save changes, and now the image will render properly. I had to do this by hand with SEVERAL HUNDRED IMAGES. Please fix this.

I looked at the metadata of the files in Photos. In the iOS metadata the PixelWidth and PixelHeight are 160 and 120, which is probably the size of the low res thumbnail stored with the DNG, padded with black pixels at the top. I don't know if Lightroom is doing anything with those values, which do imply a 4:3 aspect ratio.